This study investigates the acoustic correlates of word stress in Estonian. It forms part of a broader international collaboration the aim of which is to develop a universal language independent model for evaluating lexical stress regardless of the phonological structure of a given language. To this aim the characteristics of word stress in a range of languages is studied using unified methodology. For the present study, four acoustic measures were analysed as a function of speaking style and stress: vowel duration, F0 mean, F0 standard deviation, and spectral emphasis. The results show that the strongest correlate of style and stress in Estonian is vowel duration, but stress has a strong interaction with the Estonian three-way quantity system.